1. Field of Use
This invention relates generally to locking means for relatively movable boom sections of a multisection telescopic boom of a mobile crane.
2. Description of the Prior Art
Some mobile cranes have a multisection telescopic boom and a jib attachable or swingable into a position at the end of the boom to extend its working length. In some cases the jib is permanently connected to the boom and is swingable into and out of working position. In other cases the jib is completely detechable and is stored alongside the telescoped boom during road transport but can be readied for use by pivotally connecting the base end of the jib to the point end of the boom, whereupon the jib is swung into alignment with the boom secured in place. U.S. Pat. Nos. 3,366,250, 3,698,569, 3,785,505 and 3,830,376 exemplify boom and jib arrangements of the aforesaid types. In the aforementioned patents where a multisection telescopic boom is employed, no provision is made to guard against accidental telescoping of extended boom sections under the weight of the jib in the event of a hydraulic system failure, for example.